The power fuel supply system of an internal combustion engine carburetor supplies additional fuel to the induction passages resulting in a richer mixture required for increased power during vehicle acceleration or any time there is a heavy loading of the engine. One known type of power valve system is operated by intake manifold vacuum acting on a small piston or diaphragm. The piston actuates the power valve when the vacuum decreases during heavy loading or acceleration of the engine.
It has been found that improved drivability and economy and more precise control over engine emissions can be achieved by providing means which open the power valve in response to both intake manifold vacuum and intake air temperature. It is also an object of this invention to provide a power fuel supply system that is employed earlier (at a lesser vacuum decay) when the engine is cold than when it is warmed. Further, this invention provides a power valve control means that is adjustable to vary the relative power valve opening times of cold versus warm engines. Finally, it is an object of this invention to provide a power valve as described above which may be incorporated in carburetors of existing designs without major structural modifications.
Power valve control apparatus constructed in accordance with this invention includes a vacuum motor which displaces the movable element of an internal combustion engine carburetor power valve in response to changes in intake manifold vacuum. The vacuum passage interconnecting the vacuum motor and the source of intake manifold vacuum includes a temperature sensitive valve which opens in response to changes in induction air temperatures to bleed or vent the vacuum passage to the atmosphere.